1. Field of the Invention
The present invention is directed to a curve input system that inputs curves using a physical flexible tape and, more particularly, to a system that inputs and manipulates a multiple degree of freedom virtual curve responsive to the multiple degrees of freedom of the flexible tape.
2. Description of the Related Art
In 3D (three-dimensional) computer graphics modeling, curves are the quintessential primitive for constructing and manipulating surfaces. Successful 3D modeling is largely based on producing the right set of curves which ultimately give rise to the desired 3D shape. Thus, techniques for developing and controlling curve shapes are an important issue.
Most current interactive curve manipulation techniques require that the user, to some extent, work with the mathematical definition of a curve to control its shape. For example, curves are created and controlled by virtual techniques, such as by controlling vertex positioning and adjusting curve continuity and tangency.
In the design industry, traditional physical techniques such as clay modeling and paper drawings are still very popular. In these techniques, the clay or paper curve itself is manipulated directly by copying preshaped physical curves (e.g., french curve templates) or using physical tools which flex to produce curves (e.g., flexible steels).
Because virtual manipulation and physical manipulation of curves are so different, a designer's physical modeling skills do not wholly transfer to virtual modeling. For example, a designer can express a particular shape using a flexible french curve by simply bending the french curve. However, with a virtual curve it may not be clear how the control vertices need to be placed to attain this shape.
Certain physical objects can also quickly produce curves and surfaces that are hard to create using virtual techniques. For example, the affordances of spring steels are exploited by clay autobody sculptors who use large spring steel rulers, flexed into shape using both hands, to smoothly sweep out a curved surface on clay.
Obviously, both virtual and physical curve modeling have their own pros and cons. What is needed is a system that combines virtual and physical curve creation and control techniques.